Voltage regulator tube starter



Sept. 2'7, 1949. R. w. LEE ETAL 2,483,386

VOLTAGE REGULATOR TUBE STARTER Filed Dec. 9, 1948 Amp/1770f 1'7 I F/ 34 y Amp/MAW- fi'(. :fi

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nven or 2/6/744160 w 455 l [AVA/0N0 4. GAE/M4 Patented Sept. 27, 1949 VOLTAGE REGULATORTTUBE STARTER Richard; W.- Lee and-Raymond L. Garman, Pleas- ;an-tville, N. .Y., assignors .to- Generallrecision Laboratory Incorporated, a-corporationof New :York

Application December 9, 1948, Serial No. 64,356

,8; Claims. 7:1 This: invention relates to-a starter for electronic voltage. regulator. tubes employed in regulating direct voltage-power, supply circuits.

The purpose :of. this-invention is to vfacilitate the starting of electronic: voltage regulator tubes,

under lowv voltage conditions.

some types of equipment employing .electronic-voltage regulator tubes tdmaintain constancy-of supply voltage the availablevoltage input is limited, so that :to: maintain a reasonably than their operating voltage, $0,v that when fired 11 from a rectifying power supply operated from alternating/direct cur-rent (A.C./D.C.) mains .of

the usual. house lighting circuits of: nominally V 110 .to 125 volts, the maximum feasible .regulated voltage. has been materially lower. design for general use extreme variations of lighting circuits between 100 to 140 volts must be anticipated, voltage regulator circuits have heretofore .had, to bedesigned to fire on lighting voltages as low as 100 volts. This entails ajdirect current rectifier output of not over'90 volts and a regulated output materially lower in the usual rectifier designs which operate from a "direct current main and as regards rectifiers operating from alternating current mains through step-up power transformers th excess of starting voltage over operating voltage represents a similar loss in elficiency.

:This invention permits the use oi-voltage regulator tubes in such cases-producingregulated voltages nearly as high as the rectifier output voltages, and fires the tubes by superimposing on the tube input voltage another voltage so that the sum of the two voltages. starts the tube. The last-mentioned voltage thereupon falls to a low value and does not interfere with the normal functioning of the operatingvoltage regulator tube orof theusing equipment.

This invention is particularly applicable-to talking motion picture projectors which employ Since in .a

supersonic frequency current to light theexciter lamp filament, because the supersonic frequency supply voltage can readily be used for helping to start the voltage regulator tube in addition to its regular function. V

This invention willbemore readily understood from the following detailed description, considered together withthe attached drawing in which:

Figure Lillustrates schematically the circuit embodying the invention and employing resistame-capacitance coupling.

Figure 2 illustrates a circuit employing inductive coupling.

In vFig. 1 a talking motion picture film, exciter lamp, photoelectric'cell, amplifier and speaker are arranged to represent a conventional moving picture sound reproduction system.

An exciter lamp. l2 emits. light which in passing through the sound track ofa film strip H is modulated by the varying photographic record thereof before being impressed on the cathode it of a photocell l4. Theanode i6 is energized by a source of rectified and filtered potential diagrammatically illustrated by the terminals 33, 35 through a high resistance 2!. The potential is regulated by a voltage regulator tube 23 in series'with aballast resistor 22 across the power supply. The potential variations produced across 5 the resistor 2 l :as a resultofthe-light fluctuations impinging on the cathode l3-are impressed on the inputof --a conventional audio amplifier l3 througha blocking condenser it connected to the anode side of resistor 21. .A loudspeaker-l9 ,1 is connected to the output of theamplifier i 8 and serves to convert the amplified electrical signals toaudible sound variations.

Inthe embodiment disclosed theexciter lamp l2 isindicatedas being-energized by-a sourceof alternating current Whose frequency lSELbOVGIthG rangeof-audibili-ty of the human ear. Such an arrangement assures that the light fluctuations which may result from such alternating current energization of-theexciter lamp will be at a frequencywhich is not perceptibleand hence do not afiect the-sound reproduction as far as the ear is concerned.

To obtain --such highfrequency energization thereisprovided an oscillator: 29'consisting of a 1' thermionic tube el and itsassociated tank circuit whichmay operate at a Irequencyof sayxBG kilocycles. The output'ofthis oscillator:..is gill-.- ductively. coupled. to the filament ofthe exciter lamp l 2:by,means.-1ofi the transformer; 33, and. cable 34.

In order that it may be assured that the voltage regulator tube 23 will fire under low voltage conditions and thus exercise its regulating function over the power supply, a fraction of the output voltage of the oscillator 29 is superimposed on the rectified and filtered voltage available at the power supply terminals 33, 35.

To this end a circuit comprising a resistor 28, condenser 21 and a parallel resonant circuit 4| consisting of the inductor 3i and condenser 32 is connected between the plate 33 of the tube 31 and the positive terminal 33 of the potential supply source. The resonant circuit 4| is tuned to the frequency of the oscillator 29 and since this circuit in series with the condenser 21 and resistance 28 is eiiectively in shunt to the plate coil 33 of the oscillator, substantially the full potential developed across the coil 38 is impressed on this circuit. The resonating efficiency (Q) of the resonant circuit Al is made of a sufficient value so that while it is not so high as to require critical values of inductance and capacity to maintain resonance with the oscillator nevertheless the current flow through resistance 23 is low and substantially the full voltage generated in the plate coil 38 is developed across the resonant circuit 41. For example, the R. M. S. voltage drop across this circuit for a particular volt-age regulator tube should be in the neighborhood of 30 volts. This voltage drop is in series with the supply potential as far as the regulator tube 23 is concerned so that the potential impressed thereon is the sum of the potential available between terminals 33 and 35 and the potential drop across the resonant circuit 4!. When, therefore, as frequently happens the line voltage drops to such a low value as to be insuificient to result in the firing of the regulator tube 23, nevertheless the added potential introduced by the resonant circuit total voltage impressed thereon above the firing point so that the regulator tube fires and performs its operating function.

If, for instance, the voltage regulator tube normally operates at 85 volts but requires 115 volts to start as is customary, it may well be that when the power is turned on the voltage at the lighting mains will have decreased to some low value as 100 volts which through losses in the rectifier and filter circuits would produce a voltage of approximately 90 volts across the terminals 33, 35. Under such circumstances, without the use of this artifice, the tube 23 of course could not fire and its regulating function would :be lost so that variations in line voltage would produce induced fluctuations in photocell potential resulting in improper sound reproduction. In the instant invention, however, the alternating R. M. S. potential drop of 30 volts existing across the resonant circuit 31 is added to the 90 volts available at the terminals 33 and 35 producing an effective peak voltage at the regulator tube 23 of 132 volts causing it to fire and to regulate the voltage available at the photocell anode 13 in a range of 81 to 86 volts even though the voltage at terminals 33 and 33 varies in a range of 90 to 140 volts. As soon as the tube 23 fires there is placed in effective shunt to the resonant circuit 4! a low impedance to alternating current voltage and the divisional relation between the alternating voltage drop across the resonant circuit 4| and the circuit consisting of the series connected resistor 28 and condenser 21 is changed so that the drop across the resonant circuit is reduced to approximately volts. This reduction in voltage together with 4| is sufiicient to raise the the filter circuit consisting of condenser 42 and resistor 2| connected between the anode l6 and cathode l3 of the photocell it prevents the imposition of the alternating current on the photocell and hence this high frequency signal does not icalegtaroy the regulating properties of the regulator Resistor 28 has a relatively high value commenturate with the voltage drop desired across the resonant circuit 4| when the tube 23 is unfired so that after the tube 23 has fired the oscillator is effectively decoupled from the voltage regulator circuit and the additional loading thereon is reduced to a point where it does not effect normal operation.

Several other methods of coupling the oscillator to the voltage regulator circuit could obviously be devised to accomplish the same result of firing the voltage regulator tube while not impairing the regular function of the oscillator, the photoelectric cell or of any other part of the projector equipment. For instance, in Fig. 1 condenser 21 might be omitted if resistor 28 is suitably large, or resistor 28 might be omitted if condenser 2! is suitably small.

Another method of coupling employing electromagnetic induction is shown in Fig. 2. Here a circuit similar to that'of Fig. l in all respects is shown except that the resonant circuit 41 of Fig. 1 has in Fig. 2 been moved to a position of inductive relation with the plate coil 38. The resonant circuit in the new position is shown in Fig. 2 as circuit 43, the inductive relation existing between it and the three coils associated with oscillator tube 3'! being indicated by an arrow cutting all four coils. Circuit 43 being tuned to resonance with the frequency of the oscillations generated by the circuits of tube 31, and having a resonating efilciency of Q as described in connection with Fig. 1, will oscillate and produce at its terminals an alternating potential of approximately 30 volts, which will be effectively in series with the direct current potential available at terminals 33 and 35 to start the voltage regulator tube 23. Starting of this tube would then proceed as described in connection with Fig. l. Decoupling after tube 23 has fired would, however, occur somewhat differently than in the resistor-capacitor coupling case, but no less eiiectively. Coupling between coil 44 of circuit 43 and the plate coil 38 is made low, yet sufiicient under the condition of no loading or light loading to produce ample voltage at the terminals of coil 44. When coil 44 is loaded by the parallel resistance of tube 23 it will, in this loose-coupled condition, be effectively decoupled from the driving coil and its terminal voltage will fall to a low value.

What is claimed is:

1. In a device of the character described, a source of direct current potential subject to variation, a regulator tube connected to said source for producing a constant potential output regardless of potential variation of said source, a direct current utilization circuit energized by a circuit including said regulator tube, an oscillator, a resonant circuit connected in series with said regulator tube and said source of direct current potential, a circuit coupling said oscillator output to said resonant circuit including means for decoupling said oscillator and said resonant circuit when said regulator tube is rendered operative, thereby inhibiting the imposition of said oscillator output on said direct current utilization circuit.

2. A device in accordance with claim 1 in which said coupling circuit comprises an electrostatic capacitance.

3. A device in accordance with claim 1 in which said coupling circuit comprises an electrical resistance.

4. A device in accordance with claim 1 in which said coupling circuit comprises two inductors having mutual inductance.

5. A voltage regulator tube starting circuit comprising a voltage regulator" discharge tube, a source of direct voltage higher than the operating tube voltage but lower than the firing voltage of the tube, an electrical connection from one terminal of said source to one terminal of said tube, a protective resistor, an electrical connection from a first terminal of said protective resistor to the remaining terminal of said tube, an electronic generator of alternating current of a frequency above audibility, a parallel-tuned inductancecapacitance circuit tuned to the frequency of said generator, an electrical connection from the remaining terminal of said direct voltage source to a terminal of said inductance-capacitance circuit, an electrical connection from the remaining terminal of said inductance-capacitance circuit to the second terminal of said protective resistor, a coupling resistor, a coupling condenser, an electrical connection from one terminal of said coupling resistor to one terminal of said coupling condenser, an electrical connection from the remaining terminal of said coupling resistor to a high output voltage point Within said electronic generator, and an electrical connection from the remaining terminal of said coupling condenser to said second terminal of the protective resistor, whereby the peak voltage of said electronic generator output is superimposed on said direct voltage and whereby the two voltages together exceed the firing potential of said voltage regulator tube.

6. In a device of the character described, a source of direct current potential subject to variation, a regulator tube connected to said source for producing a constant potential output regardless of potential variation of said source, a direct current utilization circuit energized by a circuit including said regulator tube, an oscillator, a resonant circuit connected in series with said regulator tube and said source of direct current potential, a resistance condenser circuit connected between said oscillator output and the terminal of said resonant circuit remote from that connected to said direct current source whereby the proportionate amount of alternate current potential drop produced across said resonant circuit is greatly reduced on operation of said regulator tube.

7. In a device of the character described, a source of direct current potential subject to variation, a regulator tube connected to said source for producing a constant potential output regardless of potential variation of said source, a direct current utilization circuit energized by a circuit including said regulator tube, an oscillator, a resonant circuit connected in series with said regulator tube and said source of direct current potential, said resonant circuit including an inductance coil loosely coupled to the output of said oscillator whereby the resistance loading imposed thereon by the operation of said regulator tube effectively decouples said inductance coil and inhibits the imposition of said oscillator output on said direct current utilization circuit.

8. A starter for a voltage regulator tube connected to a source of direct current potential subject to variation, comprising an oscillator having an output coil connected in its plate circuit. a resonant circuit tuned to the frequency of the signal impressed on said output coil, a circuit connecting said resonant circuit in series with said voltage regulator tube and said source of direct current potential and a coupling circuit comprising a condenser and a resistor connected in series between one terminal of said resonant circuit and the plate terminal of said output coil.

RICHARD W. LEE. RAYMOND L. GARMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,410,702 Meyer Mar. 28, 1922 2,122,436 Pirani et al July 5, 1938 2,177,843 Seeley Oct. 31, 1939 

